Limescale is the chalky white or grey film that builds up on a sink in hard-water areas. On a composite sink it's usually easy to remove, as long as you use the right product and resist the urge to scrub it off with something abrasive. Here's how to do it without damaging the finish, and how to stop it coming back.
What limescale is, and where it builds up
Hard water carries dissolved minerals, mainly calcium and magnesium. When drops of water dry on the sink, the water evaporates and the minerals stay behind. One drop leaves an almost invisible mark, but thousands of them build up into a layer you can see and feel.
On a composite sink, limescale usually shows up first:
- around the plughole and the overflow
- directly under the tap, where it drips
- on the drainer, especially under a dish rack or where a washing-up bowl sits
- as a "tide mark" where water stands in the bottom of the bowl
Dark sinks show it most, but it builds up on white and coloured sinks too. There it makes the surface look dull and gives tea, coffee and food stains something to cling to.
First, check it really is limescale
Dry the sink completely and look at it in good light. Limescale usually feels slightly rough or chalky when dry, is worst where water sits or drips, and builds up gradually over weeks or months. Marks that are smooth, sharp-edged, or appeared suddenly after a hot pan or a spilt chemical may be damage rather than a deposit, and cleaning won't shift them. Our guide Why is my black composite sink turning white or grey? explains how to tell the difference.
Before you start
Check your sink maker's care guide if you still have it, or look it up on their website. Manufacturers' advice differs: some suggest diluted white vinegar for limescale, while others warn against particular acids, descalers or spray cleaners. If your sink is still under guarantee, follow what the manufacturer says, and always try a new product on a small, hidden area first.
You'll need: rubber gloves, eye protection such as safety glasses, a soft cloth or microfibre cloth, a non-scratch sponge or soft nylon brush, an old toothbrush, washing-up liquid, and a limescale remover that's suitable for composite sinks.
How to remove limescale from a composite sink, step by step
- Clear and wash the sink. Take out the dish rack, bowl, plug and any sponges. Wash the sink with warm water and a little washing-up liquid to remove grease and food residue, which can stop a limescale remover reaching the deposits. Rinse.
- Apply the limescale remover. If you're using Astraclean, put on gloves and eye protection, make sure the room is well ventilated (open a window or turn on the extractor fan), then spray it undiluted, evenly over the affected areas, and spread it with a soft cloth, sponge or brush. Do not breathe spray. Keep it off the tap: most taps are chrome-plated, and Astraclean isn't suitable for plated metals. If any lands on the tap, rinse it off straight away.
- Leave it to work. Follow the time on the label. For Astraclean that's 2–5 minutes, which gives it time to break down limescale and stains.
- Scrub lightly. Work in small circles with the sponge or nylon brush. Use the toothbrush around the plughole rim, the overflow and the base of the tap. Let the product do the work rather than pressing hard.
- Rinse thoroughly. Rinse the whole sink with warm, clean water, including the grooves of the drainer and around the plughole, so no product is left behind.
- Dry it and check. Dry the sink with a clean cloth and look again. Limescale is much easier to see on a dry sink. If patches remain, repeat the steps, or leave the product on a little longer before scrubbing.
Stubborn, thick limescale
Heavy build-up that has been there for months rarely comes off in one go. Two or three light rounds are far better for the sink than one hard scrub. Work on one area at a time, such as the plughole, then the drainer, then the bowl. If the strainer or plug basket lifts out, clean it separately. Never chip at limescale with a knife or scraper, because it's easy to gouge the surface underneath.
Can I use vinegar instead?
Possibly. Several sink makers suggest diluted white vinegar for light limescale, usually mixed with water, applied briefly and then rinsed off thoroughly. Others advise against acids, so check your manufacturer's guidance first. Never leave vinegar or any other cleaner sitting on the sink for longer than recommended. If vinegar isn't shifting it, or you'd rather use a product made for the job, Astraclean is formulated specifically for composite, granite and quartz sinks.
What to avoid
- Wire wool, metal scourers, abrasive pads, scouring powders and creams. They scratch and dull a composite surface, and fine scratches then trap even more limescale.
- Bleach, drain unblockers, oven cleaner and strong solvents. Many sink makers warn that these can discolour or mark composite. Bleach doesn't remove limescale anyway.
- Mixing products. Never mix a limescale remover with bleach or any other cleaner.
- Kettle and heavy-duty descalers that aren't meant for sinks, unless your sink maker says they're fine.
How to stop limescale coming back
- Rinse and dry. A quick wipe with a dry microfibre cloth after the last washing-up of the day is the most useful habit of all.
- Don't leave things wet in the sink. Damp sponges, cloths, a washing-up bowl or a dish rack all hold water against the surface.
- Clean little and often. A light clean when you first notice a dull film is much easier than tackling a thick crust later.
- Check your water. Your water supplier's website will tell you how hard the water is at your postcode. In very hard-water areas, a water softener cuts limescale throughout the house.
Frequently asked questions
Why does limescale show up so much on black sinks?
Limescale is white or pale grey, so it stands out sharply against a dark surface. A black or anthracite sink in a hard-water area can start to look chalky within weeks if it's often left wet. The same deposits build up on light-coloured sinks too, but they're harder to see.
How often should I descale my composite sink?
It depends on how hard your water is and how much you use the sink. Rather than following a fixed schedule, tackle it when you first notice a dull or chalky film. Drying the sink after use means you'll need to do it far less often.
Can limescale damage a composite sink?
Limescale sits on the surface rather than eating into it, but it makes the sink look dull and gives stains something to grip. The bigger risk is how it's removed: scrubbing with abrasive pads or harsh chemicals can scratch or discolour the finish for good.
Can I use Astraclean on my tap?
No. Astraclean isn't suitable for plated metals, and most kitchen taps are chrome-plated. Keep it off the tap, rinse off any overspray straight away, and clean the tap with a soft cloth and washing-up liquid instead.